Ian Waters is one of those behind the community petition calling on the NSW government to use 100 per cent Australian steel in taxpayer-funded infrastructure projects.

Mr Waters said if the mandatory minimum for Australian steel was set too low, such as a 50 per cent target, a contractor could fulfil that without ordering a single thing from BlueScope at Port Kembla.

He said this could be done by ordering reinforcing bar (also known as rebar) for concrete, which is made in Victoria and not at BlueScope.

From a price point of view, Australian rebar would be competitive with overseas product. But something like a plate welded girder, which BlueScope does make, would be more expensive than the imported product, Mr Waters said.

"Most infrastructure projects have a lot of concrete - and hence rebar - so therefore the natural thing for a contractor to do is buy enough Australian rebar to satisfy any 50 per cent rule and then buy all plate welded girders and structural steel from overseas - Port Kembla gets nothing," he said.

"The community petition asks for 100 per cent Australian steel for all NSW infrastructure projects. Very hard for people to rort, very easy to inspect for compliance, [and it] helps Port Kembla."

Mr Waters said this was not an attack on the unions' campaign for Australian steel use but was directed at politicians on both sides considering that 50 per cent was a suitable target.

"It is important to differentiate what I believe the unions are asking for compared to the politicians' statements," Mr Waters said.